Examine source code of Extension web app

{
  "manifest_version": 2,
  "name": "Just Plain",
  "version": "0.0.1",
  "description": "Copy selected text without formatting using Ctrl+C when enabled.",
  "icons": {
    "64": "icon64.png",
    "128": "icon128.png"
  },
  "permissions": [
    "storage",
    "activeTab",
    "tabs",
    "clipboardWrite"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "64": "icon64.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{20971b19-35f2-42f9-9271-232a81998548}",
      "strict_min_version": "109.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}